The present invention relates to a method and apparatus for regulating the filling force of elastically deformable particulate materials which constitute the fillers of cigarettes, cigarillos, cigars and/or other rod-shaped articles which, in turn, constitute or form part of smokers' products. More particularly, the invention relates to improvements in a method and apparatus for adjusting the feed of tobacco or other smokable particulate material in cigarette making and analogous machines for the purpose of insuring that the pressure (filling force) which the confined particulate material applies against the internal surface of the tubular wrapper of a cigarette or the like will be maintained within a desired range. Still more particularly, the invention relates to improvements in a method and apparatus for regulating the quantity of elastically deformable particulate smokable material in a stream which is about to be draped into a web of cigarette paper or the like to constitute the filler of a continuous rod which is thereupon severed to yield discrete cigarettes or analogous rod-shaped articles of unit length or multiple unit length.
The definition "smokable particulate material" embraces natural tobacco, reconstituted tobacco, artificial tobacco made of cellulose or the like, and mixtures of such substances. The material can be rendered particulate by shredding, slitting, tearing or by resorting to any other suitable comminuting technique. The rod-shaped articles which contain smokable particulate material may constitute plain or filter tipped cigars, cigarillos or cigarettes. For the sake of simplicity, the invention will be described with reference to the production of plain and filter cigarettes; however, it will be understood that the invention can be practiced in conjunction with the manufacture of any and all types of rod-shaped articles which constitute or form part of smokers' products and which involves the confinement of a continuous stream of particulate smokable material into a wrapper prior to subdivision of the resulting continuous wrapped stream into discrete rod-shaped articles of desired length.
In the manufacture of cigarettes in conventional cigarette making machines, a continuous stream of tobacco is transported lengthwise on to a wrapping station where the stream is draped into a continuous web of cigarette paper. As a rule, the stream is trimmed ahead of the wrapping station and is thereby converted into a trimmed stream or filler having a constant or substantially constant cross-sectional area. The trimming device removes the surplus from an uneven side of the stream which is transported in the groove of an endless conveyor in the form of a belt, wheel or the like. It is customary to monitor the quantity of tobacco in the stream and to change the quantity of tobacco per unit length of the stream when the monitored quantity deviates from a desired value. In many instances, the monitoring means includes a source of corpuscular radiation (e.g., a source of beta rays) and an ionization chamber. It is also known to employ monitoring devices which embody a system of capacitors. The quantity of tobacco per unit length of the stream can be changed by resorting to one or more trimming or equalizing devices with rotary knives which are movable relative to the stream to remove a variable quantity of tobacco, i.e., a quantity which is a function of the difference between the measured quantity and the desired quantity of tobacco per unit length of the stream. Alternatively, the quantity of tobacco in the stream can be varied by adjusting the distributor which draws tobacco from a source of supply and converts the withdrawn tobacco into a continuous stream. As a rule, the distributor is designed to convert withdrawn tobacco particles into a relatively wide and thin sliver or carpet which is thereupon converted into a narrow stream. The aforementioned adjustment may involve regulation of the rate at which the distributor draws tobacco particles from the source of supply.
The desired or preferred mode of operation of those parts of a cigarette making machine which form the continuous tobacco stream is such that each finished article (plain cigarette) contains a predetermined quantity for tobacco particles. The weight of the filler of a cigarette cannot be reduced below a predetermined minimum value; therefore, and in order to achieve savings in tobacco, the manufacturers of cigarettes strive to produce cigarettes wherein the weight of the tobacco filler matches or is only slightly above the minimum permissible weight. However, two cigarettes of identical weight (the weight of the tubular wrapper is negligible and can be disregarded) can exhibit different characteristics, especially as concerns the "feel" of the cigarette in the hand of a smoker. Thus, a cigarette wherein the weight of the filler matches a desired value can create the impression of a densely packed article by offering a pronounced resistance to deformation in response to the application of a pinching or squeezing force against the exterior of the wrapper. Such cigarettes are preferred by a great majority of the smokers. On the other hand, a cigarette wherein the weight of the filler is identical with the weight of a "densely packed" cigarette can create the impression of a soft and readily deformable rod whose wrapper will yield to minute finger pressure. The differences between "densely packed" and "soft" cigarettes are attributable to the condition of tobacco particles which constitute the filler. The main factor is the elasticity of tobacco particles and such elasticity, in turn, depends on the length of tobacco particles (shreds) and/or the crimp of the particles. Thus, a cigarette wherein the filler consists of relatively long shreds which exhibit a pronounced crimp will invariably create the impression of a densely packed product when compared with a cigarette having a filler of identical weight but containing a higher percentage of short tobacco and/or straight (uncrimped) shreds. Therefore, in addition to monitoring the quantity (weight) of tobacco per unit length of the stream (normally a trimmed stream or filler) which is to be draped into a web of cigarette paper, many manufacturers of tobacco further resort to measurement of the filling force of the filler of a finished cigarette, i.e., to the testing of cigarettes in order to ascertain the force with which the compacted filler of a cigarette bears against the internal surface of its wrapper. The results of such measurements are used to vary the quantity of tobacco per unit length of the stream, i.e., to insure that a cigarette whose filler consists of short tobacco and/or only slightly curled or crimped tobacoo will contain more tobacco than a cigarette wherein the filler consists of tobacco particles which are crimped and constitute or include a high percentage of long shreds. Of course, and even if the filler consists of highly satisfactory (long and crimped) tobacco particles, the quantity per unit length of the stream cannot be reduced to such an extent that the weight of the filler of a cigarette would be less than the minimum permissible weight (i.e., less than the lower threshold value of the acceptable range of weights).
The monitoring of filling force of the fillers of cigarettes is normally carried out in a laboratory. Such monitoring involves the testing of a relatively small percentage of the total output of a cigarette maker and is desirable not only when the maker processes different types of tobacco but also when the maker is set to produce a given brand of cigarettes wherein the filler consists of a given type of tobacco. The reason is that, even during such mode operation, the quality of tobacco particles which form the stream is likely to undergo rather pronounced changes, i.e., the length of the shreds and/or the extent of crimp of the shreds is likely to undergo long-range variations above and below the desired optimum value.
The presently known methods of ascertaining the filling force of fillers in cigarettes are time-consuming and must be practiced by resorting to skilled labor. Moreover, and since the samples are withdrawn at intervals and must be transferred into a laboratory, the known methods do not allow for immediate or practically immediate adjustment of the filling force when the measured filling force is unsatisfactory.
It is further known to equip a cigarette making machine with apparatus which can automatically ascertain the filling force of successive increments of a continuous tobacco stream. Reference may be had to U.S. Pat. No. 3,595,067 granted July 27, 1971 to von der Lohe et al. The apparatus which is disclosed in this patent can ascertain the filling force of a filler prior to subdivision of the wrapper filler into discrete cigarettes. Moreover, the apparatus can achieve accurate measurements of the filling force. However, the nature of measurements and of the signals which are indicative of the measured value of the filling force is such that the results of measurements cannot be readily utilized for automatic adjustment of the machine for the purpose of maintaining the filling force of the fillers of cigarettes within a desired range.